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F-correction method: F-factor charts and equations for various heat exchanger configurations, F-factor method: F-type shells: Fabrication: Failure modes of heat exchangers, Falling films, direct contact heat transfer in, Falling film evaporator: Fanno flow, Fans in air-cooled heat exchangers: Fatigue as failure mode of a heat exchanger Fatigue life, of expansion bellows, Fawcett, R Fedor's method, for critical temperature, Fenghour, A Ferritic stainless steels, as material of construction, Fick's law for diffusion, Film boiling: Film model, condenser design by Film temperature, definition of for turbulent flow over flat plate, Films in heat exchangers, Filmwise condensation: Fincotherm, heat transfer medium, Finite-difference equations: Finite difference methods: Finite-element methods: Fins (see also Extended surfaces): Fire-tube boiler, Fired heaters, Fires, room, radiation interaction phenomena in, Firsova, E V, Fixed beds: Fixed tubesheet, shell-and-tube exchangers: Flanges, mechanical design of in heat exchangers, Flash evaporation Flat absorber of thermal radiation, Flat heads: Flat plate: Flat reflector of thermal radiation, Floating head designs for shell-and-tube heat exchangers: Flooded type evaporator, in refrigeration, Flooding phenomena: Flow distribution: Flow-induced vibration, Flow regimes: Flow stream analysis method for segmentally baffled shell and tube heat exchangers, Flue gases, fouling by, Fluid elastic instability as source of flow-induced vibration, Fluid flow, lost work in, Fluid mechanics, Eulerian formulation for, Fluid-to-particle heat transfer in fluidized beds, Fluidized bed dryer: Fluidized bed gravity conveyors, Fluidized beds: Fluids: Fluorine: Fluorobenzene: Fluoroethane (Refrigerant 161): Fluoromethane (Refrigerant 41): Fluted tubes: Flux method, for modeling radiation in furnaces, Flux relationships in heat exchangers, Fogging in condensation Food processing, fouling of heat exchangers in, Forced flow reboilers: Formaldehyde: Formamide: Formic acid: Forster and Zuber correlation for nucleate boiling, Fouling, Foam systems, heat transfer in, Four phase flows, examples, Fourier law for conduction Fourier number (Fo): Frames for plate heat exchangers, France, guide to national practice for mechanical design, Free convection: Free-fall velocity, of particles, Free-stream turbulence, effect on flow over cylinders, Freeze protection of air-cooled heat exchangers, Freezing, of condensate in condensers Fresnel relations in reflection of radiation, Fretting corrosion, Friction factor: Friction multipliers in gas-liquid flow: Friction velocity, definition, Friedel correlation for frictional pressure gradient in straight channels, Froude number: Fuels, properties of, Fuller, R K, Furan: Furfural: Furnaces: Fusion welding, of tubes into tubesheets in shell-and-tube heat exchangers,

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F-correction method: F-factor charts and equations for various heat exchanger configurations, F-factor method: F-type shells: Fabrication: Failure modes of heat exchangers, Falling films, direct contact heat transfer in, Falling film evaporator: Fanno flow, Fans in air-cooled heat exchangers: Fatigue as failure mode of a heat exchanger Fatigue life, of expansion bellows, Fawcett, R Fedor's method, for critical temperature, Fenghour, A Ferritic stainless steels, as material of construction, Fick's law for diffusion, Film boiling: Film model, condenser design by Film temperature, definition of for turbulent flow over flat plate, Films in heat exchangers, Filmwise condensation: Fincotherm, heat transfer medium, Finite-difference equations: Finite difference methods: Finite-element methods: Fins (see also Extended surfaces): Fire-tube boiler, Fired heaters, Fires, room, radiation interaction phenomena in, Firsova, E V, Fixed beds: Fixed tubesheet, shell-and-tube exchangers: Flanges, mechanical design of in heat exchangers, Flash evaporation Flat absorber of thermal radiation, Flat heads: Flat plate: Flat reflector of thermal radiation, Floating head designs for shell-and-tube heat exchangers: Flooded type evaporator, in refrigeration, Flooding phenomena: Flow distribution: Flow-induced vibration, Flow regimes: Flow stream analysis method for segmentally baffled shell and tube heat exchangers, Flue gases, fouling by, Fluid elastic instability as source of flow-induced vibration, Fluid flow, lost work in, Fluid mechanics, Eulerian formulation for, Fluid-to-particle heat transfer in fluidized beds, Fluidized bed dryer: Fluidized bed gravity conveyors, Fluidized beds: Fluids: Fluorine: Fluorobenzene: Fluoroethane (Refrigerant 161): Fluoromethane (Refrigerant 41): Fluted tubes: Flux method, for modeling radiation in furnaces, Flux relationships in heat exchangers, Fogging in condensation Food processing, fouling of heat exchangers in, Forced flow reboilers: Formaldehyde: Formamide: Formic acid: Forster and Zuber correlation for nucleate boiling, Fouling, Foam systems, heat transfer in, Four phase flows, examples, Fourier law for conduction Fourier number (Fo): Frames for plate heat exchangers, France, guide to national practice for mechanical design, Free convection: Free-fall velocity, of particles, Free-stream turbulence, effect on flow over cylinders, Freeze protection of air-cooled heat exchangers, Freezing, of condensate in condensers Fresnel relations in reflection of radiation, Fretting corrosion, Friction factor: Friction multipliers in gas-liquid flow: Friction velocity, definition, Friedel correlation for frictional pressure gradient in straight channels, Froude number: Fuels, properties of, Fuller, R K, Furan: Furfural: Furnaces: Fusion welding, of tubes into tubesheets in shell-and-tube heat exchangers,
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Problems with Condensers

DOI 10.1615/hedhme.a.000369

3.18.4 Problems with condensers

There are several possible causes of poor thermal performance of a condenser, as discussed below. Fouling, common to all beat exchangers, is not included, as this is not likely to be a problem except when the coolant is dirty water (see Section 367E). The problems discussed may lead to a serious reduction in the rate of beat transfer. Further information is given by K. J. Bell in Taborek (1993) and in Section 264 of HEDH.

A. Temperature difference

The saturation temperature of a condensing stream depends on its pressure and composition. Consequently if the pressure drop exceeds the predicted amount, the temperature difference, and hence the rate of heat transfer, will be less than that predicted. Excessive pressure drop may occur in the vapour inlet nozzle or where the vapour first enters the condensing region. The problem is especially difficult with shell-side condensation of steam under vacuum.

Similarly if the condensing stream contains more incondensable gases than was anticipated, the saturation temperature will be less than was anticipated and again the rate of beat transfer will be reduced. A stream of vapours specified as being free of any gases may in reality contain small traces of gas that will increase to quite a high condensation at outlet, where the temperature difference is at its lowest; this leads to a considerable reduction in the local heat flux, due to reductions both in the temperature difference and in the beat transfer coefficient. In particular, vacuum steam condensers may fail in their performance as a result of an excessive amount of air leaking into the steam.

In a multi-component condensing stream, the temperature profile must be carefully specified, especially if there is a "temperature pinch" in the condenser, i.e. a point where the temperature difference is considerably less than elsewhere. A change in process conditions may lead to a reduction in the saturation temperature, with consequent loss in beat flux.

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